Nonlinear coupling mechanical model for large stroke magnetic-based multistable mechanisms

• A novel tristable mechanism is designed with magnetic–mechanical coupled structures.
• The interaction between large deformation mechanics and magnetic field is analyzed.
• The tristable mechanism integrates the character of constant-force generation.
• The tristability can be adjusted to other multistability.

In the previous model for small deformation multistable mechanisms, the axial displacement induced by structural vertical deflection is very small and has not been considered. However, for large deformation magnetic based multistable mechanisms, such axial displacement can directly result in the great deviation in predicting the nonlinear magnetic coupling mechanics. To enlarge the multistability design space, an accurate mathematical model was established for analyzing the nonlinear magnetic–mechanical coupling mechanics. To demonstrate the multistability analyzing procedure, a rotation constrained tristable mechanism was introduced which is also called mechanical memory element that can remember three different mechanical states including structural configurations, stable positions, and threshold triggering forces. By theoretically analyzing the influence of the large deformation induced position variation of multiple magnets on the magnetic field distribution and strength, the nonlinear force-displacement characteristic was obtained numerically, which was in good agreement with experimental results, thus validating the feasibility and practicability of the proposed nonlinear coupling mechanical model. Additionally, the multistable features such as stable positions, threshold forces and motion modes can be adjusted in a wide range for switching applications by just adjusting the magnets' arrangement.

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